In recent years, nitride semiconductor light emitting devices such as a blue light emitting diode (LED), a laser diode or the like, using nitride semiconductor, have been in practical use, and here a multi quantum well structure is employed in order to enhance light emitting efficiency at an active layer to achieve high luminance and high output. As shown, for example, in FIG. 4, in the LED emitting blue light using nitride semiconductor, a semiconductor lamination portion 36 is formed by laminating semiconductor layers, on a sapphire substrate 31, by a MOCVD method. The semiconductor lamination portion 36 includes a low temperature buffer layer 32 made of GaN or the like, an n-type layer 33 made of GaN or the like, a multi quantum well (MQW) active layer (light emitting layer) 34 formed by laminating alternately well layers 37 made of a material which has a smaller band gap energy than that of the n-type layer 33 and decides a wavelength of emitted light, such as, for example, InGaN based (which means that a ratio of In to Ga can be varied variously and the same applies hereinafter) compound semiconductor, and barrier layers 38 made of GaN or AlInGaN based (which means that a ratio of Al, In and Ga can be varied variously and the same applies hereinafter) compound semiconductor, and a p-type layer 35 made of GaN or the like. Then, a p-side electrode 41 is provided on a surface thereof interposing a light transmitting conductive layer 40, and an n-side electrode 42 is provided on a surface of the n-type layer 33 exposed by etching a part of the semiconductor lamination portion 36 laminated.
In addition, a semiconductor layer having still larger band gap energy such as an AlGaN based (which means that a ratio of Al to Ga can be varied variously and the same applies hereinafter) compound or the like may be used on the active layer side of the n-type layer 33 and the p-type layer 35 in order to increase an effect of carrier confinement (cf. for example PATENT DOCUMENT 1).    PATENT DOCUMENT 1: Japanese Patent Application Laid-Open No. H10-173222 (cf. FIG. 1)